Motor vehicles that use an electric motor as a drive engine or a traction engine have already been proposed in the prior art. On the one hand, so-called hybrid motor vehicles are known, in which a combustion engine is also present and a purely electrical operation is provided only temporarily. On the other hand, however, there exist all-electric vehicles that are also called battery electric vehicles (BEV). Whereas conventional braking systems of motor vehicles utilize the drag power of the combustion engine for slowing down the motor vehicle, in the case of all-electric vehicles or also in motor vehicles that are purely electrically operated only temporarily, the drag power of the combustion engine ceases to exist, without replacement. In this case, it has been proposed to compensate for this lack of possibility for slowing down by recuperation from the electric motor. Therefore, in this case, the electric motor is operated by a generator and feeds electrical power into the on-board high-voltage system, which can be utilized, for example, in order to charge a high-voltage battery for supplying the on-board high-voltage system, and also to satisfy the power requirement of other consumers that are connected to the on-board high-voltage system of the motor vehicle, for example, the compressors of air-conditioning systems. Here, for example, a voltage equal to or greater than 48 V can be understood as high voltage.
If, however, the motor vehicle is found in a state in which no electrical power or clearly less electrical power than the demanded braking power required in the on-board high-voltage system, thus, for example, when the high-voltage battery is almost completely charged or is completely charged, the possibility of providing braking power by recuperation is eliminated, at least partially or even completely.
Consequently, since the possibility of recuperation cannot be ensured in the known at least temporarily purely electrically operated motor vehicles, and in particular all-electric vehicles, a sufficient braking power would be ensured only by a larger dimensioned braking system and/or a more complex brake cooling. Larger dimensioned braking systems entail higher costs as well as a heavier vehicle weight, so that, in turn, the entire vehicle efficiency is negatively influenced. Also, the tire scheme is limited. A complex brake cooling is also accompanied by higher costs. Additional brake cooling channels also increase the air resistance coefficient (cw value), which leads to higher electrical consumption and thus to a lower total vehicle efficiency, and finally to shorter travel ranges.